Hi big C: You can keep the parallelogram accuracy good-enough by assuring two things: First, that both the central pivot bracket holes and the upper bracket holes share the same offset relationships. Using one as a drilling jig for the other can help keep the hole spacing and offset from vertical (if horizontal displacement is used) identical. The other is to make sure the hole spacing in the arms themselves is identical. Drill one arm first, then use it as a drilling guide for the other, that way the spacing is the same on both arms. For both the arm and bracket drilling procedures, clamp them together to keep them from shifting during drilling. Make sure you drill the holes square to the assembly. A drill press helps. For a central azimuth pivot, I resorted to Dobsonian technology. The central pivot bracket uses a solid block of hardwood with a 3/8" hole bored all the way through it. The bottom of the block has a piece of Ebony Star glued to it, and this in turn rides on a ring of Teflon. I hacksaw the head off of a 4" long carriage bolt and bolt it to the top of the tripod with the 1" threaded section. The unthreaded section then serves as the pivot bolt and the azimuth bracket is slid over the top of it. I'll send you some images shortly. The bolt is from the hardware store and I have lots of Teflon and Ebony star if you can use the method.
From: Canopus56 <canopus56@yahoo.com> Another test of two-user convenience (that mine mount fails) is how finely the parallelogram is fabricated. With good machining, I understand that when the mount is slewed to a new user at a different height, it should remain reasonably on target, e.g. - "reasonably" meaning within a few degrees.
Another problem that I failed to solve in fabricating my parallelogram bino mount was off-the-shelf hardware that would allow a rotating base. Chuck, what solution did you use?
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